Wednesday, November 2, 2011

Parallel transaction recovery and SMON Monitoring

A very nice article to read when SMON is the actual blocker on other Database Sessions.

Now in case the transaction rollback involves index block or when you querying the V$FAST_START_SERVERS you find only one server to be working then you may force disable the parallel rollback.

Follow these steps (If in RAC you must apply to all instances) :
1) Find SMON PID
select pid, program from v$process where program like '%SMON%';
2) on SQLPLUS as sysdba disable SMON transaction rollback/recovery

oradebug setorapid <SMON's Oracle PID>
oradebug event 10513 trace name context forever, level 2

3) Kill the PQ slaves that are doing parallel transaction recovery.

select 'alter system kill session '''||s.sid||','||s.serial#||''' immediate;', 'kill -9 '||spid
from v$session s, (select * from v$process
 where pid in (select pid from v$fast_start_servers)) p
 where s.paddr=p.addr;

4)  Disable parallel rollback
alter system set fast_start_parallel_rollback=false;
5) Enable SMON to do serial recovery again

oradebug setorapid <SMON's Oracle PID>
oradebug event 10513 trace name context off
oradebug wakeup 13
6) Use the follwoing query to verify serial recovery and estimate when it will finish

undoblockstotal "Total",
undoblocksdone "Done",
undoblockstotal-undoblocksdone "ToDo",
decode(cputime,0,'unknown',sysdate+(((undoblockstotal-undoblocksdone) / (undoblocksdone / cputime)) / 86400)) "Estimated time to complete"  
from v$fast_start_transactions;


Metalink Note Ids: 414242.1, 238507.1

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